Anthracite Briquettes Prepared with Phosphate Compounds and Silicon as Carbonaceous Reducing Agent Alternative to Coke for Yellow Phosphorus Production

Results are provided for anthracite briquette developed on basis of ligneous coal waste and phosphoric acid and metallic silicon for the application in the yellow phosphorus electric furnace as carbonaceous reducing agent. The influence of additives and their content, drying and heat-treating temperature on the compressive strength of briquettes is investigated, and the binding mechanisms by additives are discussed from XRD and SEM analysis result for the dried and heat-treated briquettes. AlPO4 produced by the reaction between ligneous coal waste and phosphoric acid unites anthracite fine tightly to impart the strength to briquette at less than 1200°C. However, aluminum phosphate decomposes at 1200°C and upward to give the briquette low strength. The formation and growth of SiC nanowire occurs at more than 1300°C to connect the anthracite fine acting as reinforcing agent. The compressive strength of anthracite briquettes prepared with 5% of ligneous coal waste, 4% of silicon and 5 of 85% phosphoric acid is 4.5 MPa after heat-treated at 1300°C and enough to use in yellow phosphorus electric furnace.